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What Hormone Causes Glucose To Be Removed From The Blood And Stored

Hormones And The Endocrine System

Hormones And The Endocrine System

Function: The co-ordination of body organs, so as to operate as part of an integrated system. The endocrine system is often compared with the nervous system, which also has the function of co- ordination and passing "instructions", but by an independent mechanism. This is achieved by the production of HORMONES ("chemical messengers"): - organic compounds (i.e. fairly complex molecules, based on carbon - often proteins, peptides, steroids/sterols [lipids] ) - produced by various glands in different parts of the body - endocrine glands, also called ductless glands (because they have no duct or tube to pipe their secretions to a release point) - instead they are transported in the blood - so they travel at the "speed of blood": slower than nervous impulses - cause longer lasting effects: gradually eliminated from body in urine - delivered by blood circulation to all parts of the body - each has a specific target organ/organs with specific receptors on their cell surfaces which detect the presence of the hormone - produced in small quantities (mg/µg/ng/pg) - often have profound physiological effects - used to stabilise the body's internal environment by regulating its physiology (i.e. have a role in homeostasis) - also co-ordinate longer term processes, e.g. sexual development, growth. Hormones have the function of controlling body processes which require several organs of the body to interact for a combined effect. For example, sexual development at puberty, and events during the menstrual cycle and pregnancy need general co-ordination over a long period of time, but the body's response to variation in levels of carbohydrate in the body, and reaction to stressful situations are much quicker responses. Hormonal responses are not as quick as nervous responses, but they can Continue reading >>

The Liver And Blood Glucose Levels

The Liver And Blood Glucose Levels

Tweet Glucose is the key source of energy for the human body. Supply of this vital nutrient is carried through the bloodstream to many of the body’s cells. The liver produces, stores and releases glucose depending on the body’s need for glucose, a monosaccharide. This is primarily indicated by the hormones insulin - the main regulator of sugar in the blood - and glucagon. In fact, the liver acts as the body’s glucose reservoir and helps to keep your circulating blood sugar levels and other body fuels steady and constant. How the liver regulates blood glucose During absorption and digestion, the carbohydrates in the food you eat are reduced to their simplest form, glucose. Excess glucose is then removed from the blood, with the majority of it being converted into glycogen, the storage form of glucose, by the liver’s hepatic cells via a process called glycogenesis. Glycogenolysis When blood glucose concentration declines, the liver initiates glycogenolysis. The hepatic cells reconvert their glycogen stores into glucose, and continually release them into the blood until levels approach normal range. However, when blood glucose levels fall during a long fast, the body’s glycogen stores dwindle and additional sources of blood sugar are required. To help make up this shortfall, the liver, along with the kidneys, uses amino acids, lactic acid and glycerol to produce glucose. This process is known as gluconeogenesis. The liver may also convert other sugars such as sucrose, fructose, and galactose into glucose if your body’s glucose needs not being met by your diet. Ketones Ketones are alternative fuels that are produced by the liver from fats when sugar is in short supply. When your body’s glycogen storage runs low, the body starts conserving the sugar supplies fo Continue reading >>

Insulin Synthesis And Secretion

Insulin Synthesis And Secretion

Insulin is a small protein, with a molecular weight of about 6000 Daltons. It is composed of two chains held together by disulfide bonds. The figure to the right shows a molecular model of bovine insulin, with the A chain colored blue and the larger B chain green. You can get a better appreciation for the structure of insulin by manipulating such a model yourself. The amino acid sequence is highly conserved among vertebrates, and insulin from one mammal almost certainly is biologically active in another. Even today, many diabetic patients are treated with insulin extracted from pig pancreas. Biosynthesis of Insulin Insulin is synthesized in significant quantities only in beta cells in the pancreas. The insulin mRNA is translated as a single chain precursor called preproinsulin, and removal of its signal peptide during insertion into the endoplasmic reticulum generates proinsulin. Proinsulin consists of three domains: an amino-terminal B chain, a carboxy-terminal A chain and a connecting peptide in the middle known as the C peptide. Within the endoplasmic reticulum, proinsulin is exposed to several specific endopeptidases which excise the C peptide, thereby generating the mature form of insulin. Insulin and free C peptide are packaged in the Golgi into secretory granules which accumulate in the cytoplasm. When the beta cell is appropriately stimulated, insulin is secreted from the cell by exocytosis and diffuses into islet capillary blood. C peptide is also secreted into blood, but has no known biological activity. Control of Insulin Secretion Insulin is secreted in primarily in response to elevated blood concentrations of glucose. This makes sense because insulin is "in charge" of facilitating glucose entry into cells. Some neural stimuli (e.g. sight and taste of food) Continue reading >>

Blood Sugar Level

Blood Sugar Level

The fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day with three meals. One of the effects of a sugar-rich vs a starch-rich meal is highlighted.[1] The blood sugar level, blood sugar concentration, or blood glucose level is the amount of glucose present in the blood of humans and other animals. Glucose is a simple sugar and approximately 4 grams of glucose are present in the blood of humans at all times.[2] The body tightly regulates blood glucose levels as a part of metabolic homeostasis.[2] Glucose is stored in skeletal muscle and liver cells in the form of glycogen;[2] in fasted individuals, blood glucose is maintained at a constant level at the expense of glycogen stores in the liver and skeletal muscle.[2] In humans, glucose is the primary source of energy, and is critical for normal function, in a number of tissues,[2] particularly the human brain which consumes approximately 60% of blood glucose in fasted, sedentary individuals.[2] Glucose can be transported from the intestines or liver to other tissues in the body via the bloodstream.[2] Cellular glucose uptake is primarily regulated by insulin, a hormone produced in the pancreas.[2] Glucose levels are usually lowest in the morning, before the first meal of the day, and rise after meals for an hour or two by a few millimoles. Blood sugar levels outside the normal range may be an indicator of a medical condition. A persistently high level is referred to as hyperglycemia; low levels are referred to as hypoglycemia. Diabetes mellitus is characterized by persistent hyperglycemia from any of several causes, and is the most prominent disease related to failure of blood sugar regulation. There are different methods of testing and measuring blood sugar le Continue reading >>

Human Endocrine System

Human Endocrine System

Human endocrine system, group of ductless glands that regulate body processes by secreting chemical substances called hormones. Hormones act on nearby tissues or are carried in the bloodstream to act on specific target organs and distant tissues. Diseases of the endocrine system can result from the oversecretion or undersecretion of hormones or from the inability of target organs or tissues to respond to hormones effectively. It is important to distinguish between an endocrine gland, which discharges hormones into the bloodstream, and an exocrine gland, which secretes substances through a duct opening in a gland onto an external or internal body surface. Salivary glands and sweat glands are examples of exocrine glands. Both saliva, secreted by the salivary glands, and sweat, secreted by the sweat glands, act on local tissues near the duct openings. In contrast, the hormones secreted by endocrine glands are carried by the circulation to exert their actions on tissues remote from the site of their secretion. As far back as 3000 bce, the ancient Chinese were able to diagnose and provide effective treatments for some endocrinologic disorders. For example, seaweed, which is rich in iodine, was prescribed for the treatment of goitre (enlargement of the thyroid gland). Perhaps the earliest demonstration of direct endocrinologic intervention in humans was the castration of men who could then be relied upon, more or less, to safeguard the chastity of women living in harems. During the Middle Ages and later, the practice persisting well into the 19th century, prepubertal boys were sometimes castrated to preserve the purity of their treble voices. Castration established the testes (testicles) as the source of substances responsible for the development and maintenance of “malenes Continue reading >>

Insulinomas Faqs

Insulinomas Faqs

An insulinoma is a tumour found on the pancreas and is known as a pancreatic endocrine tumour. These tumours release the hormone insulin which can affect blood sugar levels causing hypoglycaemic (hypos) episodes. Insulinomas can be benign or malignant. Insulinomas are quite rare and less than 10% are malignant. They are more common in the fifth decade of life and there is a higher incidence in women than men. Approximately 10% have multiple tumours. Approximately 5% of insulinomas are as a result of MEN1 syndrome. Multiple endocrine neoplasia type 1 (MEN1 syndrome is an extremely rare condition caused by a faulty gene which can be inherited and causes a number of tumours to develop in the endocrine system. These tumours can be benign or malignant. If your consultant suspects that you may have MEN1 you will be offered a blood test to estimate levels of calcium and certain hormones in the blood. If the condition is confirmed you will be offered genetic counselling and a treatment plan will be designed for you. Arrangements will also be made for your children and siblings to be tested for MEN1. Insulin is a peptide hormone responsible for regulating fat and carbohydrate metabolism in the body. Insulin is produced by the pancreas, which lies behind the stomach. Insulin’s role is to remove excess glucose (sugars) from the blood which could be toxic. Once glucose levels drop to the normal range, insulin release slows down or stops. However insulinomas keep releasing insulin even when your blood sugar drops too low. High blood insulin levels cause low blood sugar levels (hypoglycaemia or hypos as they are generally known). Hypos may be mild making you feel anxious or hungry or can be severe leading to a loss of consciousness or seizures. The initial symptoms for an insulinom Continue reading >>

Blood Glucose Regulation

Blood Glucose Regulation

Blood glucose regulation involves maintaining blood glucose levels at constant levels in the face of dynamic glucose intake and energy use by the body. Glucose, shown in figure 1 is key in the energy intake of humans. On average this target range is 60-100 mg/dL for an adult although people can be asymptomatic at much more varied levels. In order to maintain this range there are two main hormones that control blood glucose levels: insulin and glucagon. Insulin is released when there are high amounts of glucose in the blood stream. Glucagon is released when there are low levels of glucose in the blood stream. There are other hormones that effect glucose regulation and are mainly controlled by the sympathetic nervous system. Blood glucose regulation is very important to the maintenance of the human body. The brain doesn’t have any energy storage of its own and as a result needs a constant flow of glucose, using about 120 grams of glucose daily or about 60% of total glucose used by the body at resting state. [1] With out proper blood glucose regulation the brain and other organs could starve leading to death. Insulin A key regulatory pathway to control blood glucose levels is the hormone insulin. Insulin is released from the beta cells in the islets of Langerhans found in the pancreas. Insulin is released when there is a high concentration of glucose in the blood stream. The beta cells know to release insulin through the fallowing pathway depicted in figure 2. [2,3]Glucose enters the cell and ATP is produce in the mitochondria through the Krebs cycle and electron transport chain. This increase in ATP causes channels to closes. These channels allow potassium cations to flow into the cell. [2,3,]With these channels closed the inside of the cell becomes more negative causin Continue reading >>

Pancreatic Hormones

Pancreatic Hormones

Pancreas is both exocrine and endocrine gland. The exocrinal part secretes pancreatic fluid into the duodenum after a meal. The endocrinal part secretes various types of hormones. These are produced by a specialized tissue in the pancreas and then released to the capillary system and reached the liver by the portal venous circulation. The specialized tissue is called islets of Langerhans. Islets of Langerhans represent approximately 1-2 % of the pancreas. Three types of cells are regonized in these islets. A cells – producing glucagon (25% of all islet cells). B cells – producing insulin (60% of all islet cells). D cells – producing somatostatin (10% of all islet cells). F cells – producing panceratic polypeptide (5% of all islet cells). Islets of Langerhans play a crucial role in carbohydrate metabolism and so in a plasma glucose concentration. It involves: Glycolysis – the anaerobic conversion of glucose to lactate. Occurs in the red blood cells, renal medulla and sceletal muscles. Glycogenesis – the synthesis of glycogen from glucose. Glucose is stored ( in liver, muscle) in the form of glycogen and this serves to maintain a constant plasma glucose concentration. Glycogenolysis – the breakdown of glycogen to glucose. Gluconeogenesis – the production of glucose from non-sugar molecules (amino acids, lactate, glycerol) Lipolysis – the breakdown of triacylglycerols into glycerol and free fatty acids. Lipogenesis – the synthesis of triacylglycerols. Pancreatic hormones are responsible for storage of fat and glucose, as glycogen, after meal. Enables the mobilisation of energy reserves as a result of food deprivation, stress, physical activity. Maintain the constant plasma glucose concentration. Promote growth. Pancreatic hormone Insulin is a peptide co Continue reading >>

The Difference In How Fructose And Glucose Affect Your Body

The Difference In How Fructose And Glucose Affect Your Body

My regular readers know that I consider agave to be a BIG enemy to health and beauty- which is very high in fructose (up to 97% fructose). It truly irks me that sly marketing makes the general public think agave is a “healthy” sweetener, and that it continues to be used in “health” products purported to be better than regular baked or other goods, as well as in many restaurants. It is not. There is a myth that exists that fructose is a “healthy” sugar while glucose is bad stuff. In fact, in recent years, there has been a rise in sweeteners that contain this “healthy” sugar, such as the dreaded agave nectar. I sincerely hope that this information (please help spread it!) makes more people aware of the differences in sugar types, and makes more people know to avoid agave at all costs. S.O.S: Save Our Skin!!! Fructose Fructose is one type of sugar molecule. It occurs naturally in fresh fruits, giving them their sweetness. Because of this, many people consider fructose “natural,” and assume that all fructose products are healthier than other types of sugar. Likewise, fructose has a low glycemic index, meaning it has minimal impact on blood glucose levels. This has made it a popular sweetener with people on low-carbohydrate and low-glycemic diets, which aim to minimize blood glucose levels in order to minimize insulin release. But the glycemic index is not the sole determining factor in whether a sweetener is “healthy” or desirable to use. Because fructose is very sweet, fruit contains relatively small amounts, providing your body with just a little bit of the sugar, which is very easily handled. If people continued to eat fructose only in fruit and occasionally honey as our ancestors did, the body would easily process it without any problems. Unfortu Continue reading >>

What Happens To Food In Your Body?

What Happens To Food In Your Body?

Just thinking about eating causes your body to start secreting insulin, a hormone that helps keep blood sugar (glucose) under control. Insulin is made by the pancreas. As you eat, more insulin is released, in response to the carbohydrates in the meal. Insulin is released when you eat protein-rich foods, but at a slower rate. If your pancreas is functioning properly, the amount of carbohydrates in what you’re eating usually determines how much insulin is released. As you digest carbohydrates, they go into the blood stream as glucose. To keep blood sugar levels under control, insulin signals the cells in your body to take in glucose from the blood stream. The cells use some of glucose for energy and store some for later use. The way glucose is stored depends on the type of cell doing the storing. Muscle cells store glucose as glycogen. Liver cells store some glucose as glycogen and convert some to fat. Fat cells store glucose as fat. As glucose is removed from the blood stream, insulin levels go down and your cells start using fat for fuel instead of glucose. This is why you can go for long stretches – overnight, for example, when you’re sleeping, without eating. Your cells rely on fat for fuel. There are two types of body fat: fatty acids and triglycerides. Fatty acids are small enough to move in and out of cells and be used as fuel for cells. Fat is stored inside fat cells as triglycerides, three fatty acids bound together. Triglycerides are too big to flow through cell membranes and so are stored for future use. Insulin also plays a major role in telling your body when to store and use fat and protein. It does this by affecting the actions of two enzymes, lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL). LPL sits on the surface of cells and pulls fat o Continue reading >>

Insulin

Insulin

History Insulin is a hormone secreted by the pancreas gland, one of the glands in the endocrine system. Insulin, working in harmony with other hormones, regulates the level of blood sugar (glucose). Endocrine glands are ductless glands; that is, they pour their products (hormones) directly into the bloodstream. The pancreas, a gland in the upper abdomen, has cells within it that secrete insulin directly into the bloodstream. An insufficient level of insulin secretion leads to high blood sugar, a disease called diabetes mellitus or, simply, diabetes. Specifically, diabetes is a metabolic disease caused by the body’s inability to use the hormone insulin to effectively convert carbohydrates into the simple sugar glucose that cells store and use to perform vital functions. Without glucose to fuel their activity, the cells use fat instead, producing ketones as a waste product. Ketones build up in blood and disrupt brain functions. Common signs of diabetes are excessive thirst, urination, and fatigue. The disease can also cause vision loss, decreased blood supply to hands and feet, pain, and skin infections. If left untreated diabetes can induce coma and cause death. Diabetes often runs in families. In the United States about 10% of the Caucasian population suffers from diabetes, and it is even more common among African-American, Mexican-American, and certain Native American groups. The sixth leading cause of death in the United States, diabetes remains a major health problem. According to the American Diabetes Association, about 20.8 million children and adults (about 7% of the U.S. population), as of 2006, suffer from diabetes mellitus. About 14.6 million people have been diagnosed with diabetes. However, about 6.2 million people (about one-third) do not know that they ha Continue reading >>

Diabetes Information Guide

Diabetes Information Guide

Diabetes Mellitus as it is known medically is a condition that is characterised by a high or elevated level of blood sugar called glucose. It translates literally to mean ‘urine sweetened with honey’, which pertains to the sweet nature of the urine of diabetic patients. Currently it is estimated to affect over 120 million people worldwide and the number is rising rapidly. Changes in Blood Glucose Levels Glucose is a vital part of our diet and is found in many different types of food. When we eat, the carbohydrates we have in our diet are broken down by enzymes in our digestive system, to the smallest unit called, glucose. Once absorbed within our bodies, glucose is broken down to provide our cells with energy to grow and repair. The enzymes that are involved in this process are called glycosylases and amylases and are produced within the α cells of the pancreas. This organ is located just behind the stomach on the left hand side of our bodies, containing 3 main types of cells, α cells, β cells and γ cells. Each of these cell types produces a different enzyme. The β cells produce insulin, whereas the γ cells are responsible for producing glucagon. Both of these enzymes are responsible for maintaining an adequate blood glucose level. When we eat a meal, within 15 minutes our body absorbs the majority of the glucose through our intestines and into our blood. This causes our blood sugar levels to rise rapidly, prompting the pancreas to release insulin into our blood. The insulin then binds to specific receptors on our liver and muscle cells, telling them to take up and store glucose, and to stop producing glucose, in the case of the liver. This enables us to store glucose as glycogen, which can then be converted back to glucose in between meals. As our blood sugar Continue reading >>

Review The Glut4 Glucose Transporter

Review The Glut4 Glucose Transporter

Figure 1. Structural Features of the Insulin-Regulated GLUT4 Glucose Transporter Protein The unique sensitivity of GLUT4 to insulin-mediated translocation appears to derive from sequences shown in the N-terminal (required phenylalanine) and COOH-terminal (required dileucine and acidic residues) regions. These sequences are likely involved in rapid internalization and sorting of GLUT4 in intracellular membranes termed GLUT4 storage vesicles (GSV), as outlined in Figure 3. See text for further details. GLUT4 Is a Key Determinant of Glucose Homeostasis A central role for GLUT4 in whole-body metabolism is strongly supported by a variety of genetically engineered mouse models where expression of the transporter is either enhanced or ablated in muscle or adipose tissue or both. The whole-body GLUT4−/− mouse itself may be less informative due to upregulation of compensatory mechanisms that may promote survival of these animals (Katz et al., 1995; Stenbit et al., 1996). However, heterozygous GLUT4+/− mice that display decreased GLUT4 protein in muscle and adipose tissue show the expected insulin resistance and propensity toward diabetes that is consistent with a major role of GLUT4 in glucose disposal (Rossetti et al., 1997; Stenbit et al., 1997; Li et al., 2000). Interestingly, overexpression of GLUT4 expression in skeletal muscle of such GLUT4+/− animals through crosses with transgenic mice normalizes insulin sensitivity and glucose tolerance (Tsao et al., 1999). Transgenic mice expressing high levels of GLUT4 in adipose tissue (Shepherd et al., 1993; Tozzo et al., 1995) or in skeletal muscle (Tsao et al., 1996, 2001) in turn are both highly insulin sensitive and glucose tolerant. Conversely, conditional depletion of GLUT4 in either adipose tissue or skeletal muscle c Continue reading >>

Glucose

Glucose

Glucose is derived from digestion of dietary carbohydrates, breakdown of glycogen in the liver (glycogenolysis) and production of glucose from amino acid precursors in the liver (gluconeogenesis). In ruminants, the main source of glucose is gluconeogenesis from volatile fatty acids (propionate) absorbed from rumen by bacterial fermentation. Glucose is the principal source of energy for mammalian cells. Uptake is mediated by a group of membrane transport proteins, called glucose transporters (GLU), some of which are insulin-dependent, e.g. GLU-4. Physiology Blood glucose concentration is influenced by hormones which facilitate its entry into or removal from the circulation. The hormones affect glucose concentrations by modifying glucose uptake by cells (for energy production), promoting or inhibiting gluconeogenesis, or affecting glycogenesis (glycogen production) and glycogenolysis and are listed below. The most important hormone involved in glucose metabolism is insulin, which enables energy use and storage and decreases blood glucose concentration. Several hormones oppose the action of insulin and, therefore, will increase blood glucose. The main hormones that mediate this effect are glucagon, growth hormone, catecholamines, and corticosteroids. The increase in blood glucose can occur through inhibition of insulin release, stimulation of glucose-yielding pathways (glycogenolysis, gluconeogenesis), or decrease of glucose uptake or use by tissues. Table 1 below summarizes these effects. Collectively, increases in these insulin opposing hormones can induce a state of insulin resistance. Insulin resistance can also be mediated by inflammatory cytokines (tumor necrosis factor-α [TNF-α]), obesity and pregnancy. Inflammatory cytokines are thought to be responsible for insu Continue reading >>

Metabolic System

Metabolic System

Metabolism is the term used to describe the many chemical reactions that are involved in the utilisation of nutrients in the body. If these reactions are investigated more closely, it will be found that they may be placed into one of two categories known as anabolism (building more complex compounds from the simple ones resulting from digestion) and metabolism (breaking down of these complex compounds to produce energy for normal body functions). These reactions are quite complex and the important aspects only are covered here. Discussion will be confined to the three major dietary inclusions of carbohydrates, fat and protein. The minerals, vitamins and other nutrients are not discussed. The only carbohydrate found in the blood is glucose. A certain concentration of glucose is necessary in the blood stream for normal activity. Any excess glucose is stored. If the body is glucose deficient, body reserves are then used to make up the supply to demand. This means that when carbohydrates are digested they are broken down to glucose. Glucose is stored as glycogen in the liver and large quantities are also found in the muscles. Excess glucose can also be converted to fat for storage. Glucose is oxidised to produce energy, and carbon dioxide and water are produced as by-products. A small amount of carbohydrate is also found in cell protoplasm. After eating, the complex carbohydrates are broken down into glucose that is absorbed from the alimentary canal into the capillaries of the villi of the small intestine and then into the portal vein en-route to the liver. Here some of it is stored as glycogen. The remainder enters the systemic circulatory system (blood system for the body) and is transported to the tissues. Its presence in the blood causes an increase in the blood sugar Continue reading >>

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